The action of estrogen on two sex hormone-induced and supported Syrian hamster tumors is under investigation. The integumentary scent gland tumor (stilbestrol/testosterone induced) has been found to be of possible Schwann cell/perineural epithelium origin. Lactic dehydrogenase isozyme pattern of the tumor changes when stilbestrol treatment of the tumor is stopped (the MLDH isozyme decreases in concentration). Cloning experiments will be used to help to determine if there is more than one cell type in the tumor. The stilbestrol-induced renal tumor shows a different glucose-6-phosphate dehydrogenase isozyme pattern from that of two autonomous renal variants and a spontaneous renal tumor. C-type RNA viruses have been noted in electron micrographs of one autonomous variant and the spontaneous renal tumors are being examined for virus particles. Group specific antigen tests for the virus will be done on the primary tumor.